Losing feathers on neck!

[Winkiesfirstchicks]

Can someone help me! Is this part of getting real feathers in? It was not like this yesterday but her feathers have been coming in all at once instead of gradually like the others. She’s also the runt and I was worried about a little loose stool so please tell me if I need to isolate her! Or she’s getting bullied

 

[Winkiesfirstchicks]

Also first time mistake…when I ordered my chicks I checked yes for vaccinate I didn’t realized they were only vaccinated for mereks until recently so I started feeding medicated feed. Can someone tell me what to look out for with coicidi(you know) with the loose stool do I only have to worry if it has blood. Everyone’s acting fine and eating. It’s still formed but more watery then the others